|Publication number||US7042449 B2|
|Application number||US 10/183,432|
|Publication date||May 9, 2006|
|Filing date||Jun 28, 2002|
|Priority date||Jun 28, 2002|
|Also published as||US20040001110|
|Publication number||10183432, 183432, US 7042449 B2, US 7042449B2, US-B2-7042449, US7042449 B2, US7042449B2|
|Original Assignee||Autodesk Canada Co.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (2), Referenced by (12), Classifications (20), Legal Events (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention is directed to a system for orbital and volumetric navigation that can be used for three-dimensional tasks such as painting and viewing. More particularly, the present invention allows a user to change a viewpoint of an object by essentially pushing and tumbling the object.
2. Description of the Related Art
Three dimensional viewing systems usually include provisions for manipulating a view. Manipulation is generally designed to affect 6 degrees of freedom of a view; 3 for the view direction, and 3 for the view point or position. In the past, two approaches have been used for manipulating a view. First, separate panning, zooming, and tumbling or rotating operations have been assigned to different input controls or modes. Because of the high number of different manipulation actions, and because of the number of viewing parameters affected by those manipulations, it has been difficult to effectively and smoothly manipulate a view. Camera manipulation has generally taken one of two approaches.
A first approach to camera manipulation has been mode-based or multi-control manipulation, where different modes or controls are associated with different operations. For example, a mouse may have extra buttons, and the buttons will switch between different manipulation modes. For example, Button1+drag might control zooming (moving the camera along its camera direction), Button2+drag might control panning (translating the view), and Button3+drag might control tumble or rotation about a single fixed point, often a center or gravity point.
A second approach has been to use complex input devices that can move in three dimensions or otherwise provide greater three-dimensional input data. These devices include, for example, three-dimensional pucks, “space” mice, and other similar devices that are moved in three dimensions. Three-dimensional input devices often require two-handed control, are expensive, require training, or may require resources not available to a typical user with a typical computer workstation. What is needed is a system for manipulating a virtual navigation tool (e.g a camera) or multiple parameters of a virtual tool with a simple input device or input data, without having to toggle between different manipulation controls or modes, and without requiring expensive non-standard input devices.
It is an aspect of the present invention to provide a system for manipulating parameters of a virtual camera with a simple input device or input data, without the use of different manipulation controls, and without the use of non-standard three-dimensional input devices.
It is an aspect of the present invention to provide a navigation system which can simultaneously control the panning, zooming, and tumbling of a view using only a two-dimensional input device or input data.
It is another aspect of the present invention to provide for simultaneous panning, zooming, and tumbling without switching between corresponding modes.
It is an additional aspect of the present invention to use two-dimensional input data to allow a user to simulate object-centric manipulation of an object or view.
It is also an aspect of the present invention to move a camera or brush about a model while keeping it a consistent distance from the “surface” of the object.
It is a further aspect of the present invention to move a camera or brush about a model while keeping it facing the object and while keeping it a consistent distance from the “surface” of the object.
It is an aspect of the present invention to use a present position of a camera, two-dimensional input data, and a view direction of the camera to determine a new view of the camera.
It is also an aspect of the present invention to use a closest point of a model to a tool, to obtain a normal or model-facing orientation of the tool, or to keep a tool moved by two-dimensional data a constant distance from the model.
It is an aspect of the present invention to provide a navigation system that can be used with web browsers and standard input devices to enable complete manipulation of a model displayed in the web browser, without having to change view-manipulation modes, while maintaining a relatively normal, equidistant, and centered view of the model.
It is another aspect of the present invention to smoothly navigate a camera around edges of a model.
It is another aspect of the present invention to smoothly turn a brush about a model for selection or modification.
It is another aspect of the present invention to smoothly navigate a camera towards a consistent distance from a model when initial conditions are not met or when changing focus between models.
It is another aspect of the present invention to provide a tool that can navigate independently of the underlying model class including surfaces, curves in space, clusters of points, and voxels whether they are explicitly or implicitly created.
The above aspects can be attained by a system that generates or receives a two-dimensional input, automatically pans a view of a model according to the two-dimensional input, automatically zooms the view according to the two-dimensional input, and automatically tumbles or rotates the view according to the two-dimensional input, where the panning, zooming, and tumbling are relative to a fixed point in the space of the model.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
The present invention is directed to a three-dimensional viewing system. Viewing systems, virtual views, or virtual cameras simulate what a person would see if they were placed within a virtual or three-dimensional space. A viewing system, a view, virtual eye, or virtual camera in part consists of viewing parameters, such as a view point and a viewing direction. A view point establishes the viewer's position within the space being viewed. The view point can be an origin of a coordinate system of the view, or the center of projection together with a view direction. A view direction is usually a vector defining the direction the view is pointed, and is sometimes referred to as the center of view.
A cylinder is a type of object that can be viewed with a viewing system.
As shown by the viewing of the cylinder model 120 discussed above, manipulating a view or camera to a desired view can take several different actions, which is often unwieldy (requiring switching between multiple modes) and is time consuming. Switching between modes or controls will also interrupt an operation being performed on the object, for example painting, drawing, reshaping, etc. Furthermore, in the case of a person virtually viewing or operating on a virtual workpiece (e.g. an artist virtually painting a three-dimensional model of a frog), the person would like to manipulate the model as they would a real-life model; by viewing different parts of the model surface while keeping the model virtually facing the artist and at a constant virtual viewing distance. This kind of viewing can be defined as object-centered or object-centric viewing. Considering the role of the surface of the model in viewing the model, this kind of viewing can also be defined as surface viewing; the process by which people, for example artists, have an area of constant visual focus distance and position themselves or the object (or both) to change the contents of the focal area while otherwise maintaining the focal area and distance.
With the mode-based or multi-control view manipulation, a viewer or artist must repeatedly make a series of manipulations similar to the cylinder view manipulations 126, 130, 134 shown in
According to the two-dimensional vector, the view point is two-dimensionally moved 154 in the plane defined by the direction of the initial view and the initial view point (see stage B of
After the view point is moved 154 in the plane to a second view point position, the closest point of the model to the second view point may be found by projecting rays 156 from the second view point (see stage C of
The view direction of the moved view may be set 162 to the direction of the ray that was selected 160 (see stage E of
By repeating 168 the process, for example in response to further two-dimensional mouse movement data, the model may be smoothly viewed from different points, each with generally the same focal length to the object's surface or area of interest, and while generally keeping the object facing the view. Although the surface viewing distance may be constant, zooming occurs because the distance between the view and a fixed point of the object (e.g. center) changes. Because the center of a view (view direction) is oriented to the closest point of the model, the model faces the view (is locally normal to the view direction). When the closest point does not have a well-defined normal vector (e.g. the closest point is a corner), the view moves smoothly about the closest point (corner) because each position of the view may be based on the previous view, as explained further below with reference to
When two-dimensional input data is received, the input is scaled and applied to the camera position as a two-dimensional translation 190 in the plane 192 that is normal to or specified by the initial direction 188 (the viewing vector). The translation 190 of the view is preferably made without constraint to roughly express a desired position of the camera or view. However, a radial distance constraint may be placed on this move to smoothly approach an object if the camera is initially at a significant distance from the surface or area of interest of the model. Other constraints or interpolation can be used to further smooth the movement of the view.
After the position of the view point 184 has been translated 190 to new view position 194, rays 196 are cast out from the new position 194, preferably in a direction based on the initial view direction 188. For each ray 196, a point of intersection 200 with the cube 180 is determined. The ray 196/198 that has the closest point 200/202 on the cube 180 is selected. Although the rays 196 are shown in
Ray casting is a common technique described in readily available computer graphic references. Other methods for finding a closest point on the cube 180 may also be used. Furthermore, beside the direction to a closest point, other ray casting directions may be used. For example, the rays can be weighted by their distance and combined to obtain and use an average closest direction. The ray casting direction may be based in whole or in part on the direction of movement, etc. Other algorithms or statistics can also be used to define the direction in which an area of an object faces, including pre-determined values associated with regions of a model, or by mathematical calculation, as for example when the model is a Non-Uniform Rational B-Spline (NURBS) object.
After the ray 198 with the closest point 202 has been determined, the view direction 188 is set to the direction of the ray 198 with the closest point 202, so the final view direction 188/204 faces the closest point 202. Finally, the moved view point 194 may be again moved from point 194 to final view point 194/186 so final view point 186 is original distance d from the cube 180. Although a constant distance may be used, a dynamic distance may also be used. The view distance can be dynamically set according to an area of the model, a level of surface noise, a speed of the view point, etc.
Dashed line 181 (upper left hand corner and lower right hand corner) shows the initial view 184 relative to the center 183 of the cube 180. Dashed line 195 (lower right hand corner) shows the final view 194/186 relative to the center 183. The difference between lines 181 and 195 demonstrates that, relative to the center point 183, the distance to the center point 183 has been changed (zoomed), and the direction to the center point 183 has changed (panned and rotated). With other fixed points in the three-dimensional space, the same relative changes occur.
With a process as discussed above, camera manipulations that previously required two or more buttons or input commands can be performed with a single input, such as a mouse stroke or drag. One drag or one button+drag can now simultaneously control two or three of panning, zooming (distance to center of object), and tumbling.
While the present invention can control multiple simultaneous camera actions with a two-dimensional input, these actions can also occur individually. When the camera initially faces a point on a flat surface, and moves along the flat surface to another position facing another point on the same flat surface, the process becomes a simple panning motion. In the case of moving the camera along the length of the cylinder (parallel to its axis), the cylinder is simply panned across the view (while zooming with reference to a center of the object). When the camera moves in the direction of the curvature of the cylinder, the cylinder or camera is in effect tumbling or rotating about the axis of the cylinder. Even in the case of a complex object such as a spaceship, the object stays optimally in view and facing the view as the view moves about the spaceship.
With the process of camera adjustment and movement discussed above, the camera position may be used to determine the closest point, which may then be used to determine a new camera position and direction. However, it is not necessary to couple these factors with the camera position. A new camera position may be determined independently, for example by using a pre-calculated iso-distance shell (discussed below), and its direction need not be based on its new position. For example, the camera direction can be based on the geometry of the object.
With complex objects, it is also possible, when arranging a view with the process discussed above, for two different points or areas of the object to simultaneously be closest to the view. This can cause the moving view to abruptly and unintuitively jump to an area of the object that is not contiguous with the previously viewed area of the model.
For example, if the model or object is the cup 242, and the camera is facing the outside of the cup (point A) and is moved up the cup and over the lip to the inside region of the cup, a point on the opposite side of the cup could be considered when searching for the closest point. The movement or history of the camera can be used to restrict arrangement of the camera to arrangements that result in viewing connected, adjacent, or nearby surfaces. That is to say, a smooth viewing path can be maintained. If the model consists of polygons, such a restriction can be performed using polygons. In other words, if the camera is focused on a polygon and is moved, the movement can be restricted to keep the focus of the camera on adjacent, nearby, or connected polygons.
Obscuring may also be addressed by pre-computing a shell that surrounds the object or model. Such a shell can be calculated using a process similar to the camera arrangement process discussed above. A shell can also be computed or pre-computed (in advance of navigating an object) by using conventional techniques of “shrink-wrapping” an object (wrapping a sphere around the object and moving points on the sphere closer to the object until it reaches some small distance). An iso-surface or iso-distant shell can also be used. When a shell is pre-computed, ambiguities or self-intersections (e.g. the inside of a cup) can be automatically detected and eliminated before viewing or navigating. A shell is also a convenient way to smooth out a view of a noisy surface or model. Surface distance averages or other algorithms may be used for automatic smoothing.
The distance or zoom to an object from a view has been described as constant, however, it may also be dynamically determined. When two different areas of the model are candidates for facing the camera (e.g. the inside of a cup), the viewing distance could be reduced so that only the logically contiguous area is closest to the camera. The focal distance of a view can also be dynamically changed with regions of an object. For example, if a model of the earth is viewed, an orbital-scale focal distance could be used when the view is not close to any features of the earth, and a smaller distance could be used when the view is near an area or feature, such as a mountain. The distance to the surface of the object can also be determined by the surface noise or detail of the object.
The present invention has been described with a view direction or a center of view that is typically normal to the surface or view of the object. However, the view direction need not be precisely normal for the desired viewing effect. For example, variation can be allowed to smooth out the movement or change in the view. The view direction can also be allowed to vary within a certain range to enable some camera adjustment within the range that does not pan or move the view. A “pushable” area of view (e.g. a cone) can also be used. That is to say, the present invention may also be constructed to automatically move the three-dimensional view when input data indicates that the focus point is approaching or at the edge of the displayed view or the view area (e.g. the view plane window). When the focus point reaches that point, the corresponding part of the model is automatically moved into view. In other words, the user can push at or past the edge of the view and the model can pan and zoom responsive to the push. In this way, the invention may be invoked implicitly or explicitly.
The present invention may also be provided with an “up” direction defining the “up” direction of the view. An “up” vector or direction may be used to orient the rendered image of the view, giving the effect of a consistent up-orientation of the viewer relative to the viewed model. The “up” direction may be globally set. For example, it may be set to some point effectively infinitely distant from the object being viewed. The “up” direction may also be procedurally, algorithmically, or dynamically determined. For instance, “up” may be based on a history of the arrangement of a changing view. Different regions of an object may have different local definitions of up. “Up” may be set according to a direction of movement of the camera or relative to the movement direction. “Up” can also be context sensitive, for example it can be determined according to the orientation of relevant text. Using the “up” vector, the camera can also be made to pitch and roll as it moves.
Although the focal distance to the surface of the object is preferably constant, it may also be determined dynamically. While still using only a two-dimensional input device, the zoom or viewing distance can be changed based on the speed of the camera or input device movement. For instance, if the camera accelerates or goes above a certain speed, the zoom may be made larger (similar to the orbital radius of an orbiting body increases when the body accelerates). If the camera slows down, the zoom can decrease. Other schemes for changing the zoom or using the input speed may also be used to effectuate a consistent object-centered view.
As mentioned above, if an object is not initially at a desirable viewing distance from the camera, provisions may be made to smoothly approach the object, for example by smoothly interpolating to the optimum view. Smooth motion of the camera can also be improved by providing a threshold distance defining how minimally close a potential new focus point must be to the subject being viewed. For example, the points at which rays intersect a model would be required to be within a threshold distance of the previous focus point or the view point or else the point and its corresponding ray will be ignored. It is also possible to smoothly navigate the camera over high frequency (e.g. bumpy) surfaces. This can be accomplished by, for example, the use of a weighted or average preferred view direction as discussed above. This can also be addressed with the use of a pre-computed shell, discussed in detail further below.
Although the present invention has been described in terms of moving and adjusting a camera or view of a model, the present invention can conversely be equally considered and described with reference to moving or adjusting the model with reference to or relative to the view. Similarly, the present invention may also be understood as having a focus point on the model that is a tumble or rotation center with a fixed radius (focal distance) and that dynamically moves along the surface of the object as the camera moves. It is therefore apparent that the present invention is capable of providing an object-centric view facing the object, in which the object is optimally viewed for a given operation such as virtual painting.
Although the present invention may be used interactively with an input device, it may also be used to automatically generate walkthroughs or fly-bys for automatically viewing a model without interactive camera manipulation. The present invention may be used with volumetric applications in general. Although the present invention is capable of navigating a camera around an orbital shell using two-dimensional input, the present invention is also capable of navigating through orbital paths (or paths on the shell) using one dimensional input.
Furthermore, a viewed or navigated model does not require a formally defined surface. The model or object can be or can include a cloud of points, and the surface or area of interest might be a layer or region in the cloud, rather than a surface per se. If the viewing distance is set to 0 then the surface may be painted on or the interior of a cloud may be navigated, viewed, or operated upon. A curve in three dimensions can also be viewed or navigated with the present invention.
The term “surface” is generally defined to mean the discrete surface defining a boundary between of the model. However, as discussed above, some models do not have defined boundaries (e.g. clouds), and therefore “surface” also is defined to mean a definable layer, stratum, or three-dimensional zone of a locus of elements of the model. For example, the “surface” of a cloud of points, voxels, or objects may be those elements of the cloud that are within (or beyond) a certain distance from a gravitational center or some other point or region of the cloud.
The present invention may also be used for three-dimensional view or navigation control within a web browser. With current browsers, three-dimensional views of models are manipulated with multiple controls. This can create problems such as the camera losing sight of the object or ending up in unidentifiable or irreversible positions. The present invention avoids these problems. Furthermore, because most web browsers are designed to receive and handle two-dimensional input events (e.g. mouse movement events), the present invention is well-suited for object-centric viewing or navigation within a web browser. A browser can be enhanced with a separate add-on or by direct modification.
The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
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|U.S. Classification||345/420, 345/629, 715/850, 345/649, 345/427, 345/647, 715/858, 715/849, 345/619, 715/848|
|International Classification||G06T3/00, G06F3/033, G06F3/048, G06T17/00|
|Cooperative Classification||G06T15/20, G06T19/00, G06F3/04815|
|European Classification||G06T19/00N, G06T19/00, G06F3/0481E|
|Aug 3, 2004||AS||Assignment|
Owner name: ALIAS SYSTEMS CORP., CALIFORNIA
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